Cardio pharmacology (II): Rate And Rhythm Control Flashcards
(40 cards)
Digoxin indication
Atrial fibrillation or flutter.
Heart failure
Emergency loading dose for atrial fibrillation or flutter.
Digoxin Therapeutic Range
0.7 to 2 nanogram/mL (wide inter-individual variations).
How do you start digoxin (dose)
Loading dose of 250 micrograms to 750 micrograms for 7 days followed by maintenance dose 125 micrograms-250 micrograms adjusted according to renal function and heart rate response.
What is max maintenance dose of digoxin.
(a) 250 micrograms
(b) 125 micrograms
(c) 300 micrograms
(d) 150 micrograms
(a) 250 micrograms daily
When would you suspect DigToxicity.
(a) 0.5 nanogram/mL
(b) 3.0 nanograms/mL
(c) 3.0 nanograms/L
(d)1.5 nanogram/mL in presence of hypokalemia
(e) 0.8 nanograms.
(f) 1.8 nanograms/L nanograms
(b) 3.0 nanograms/mL + (d) 1.5 nanogram/mL in presence of hypokalemia because dig toxicity is more pronounced in hypokalemia due to less competition to bind to sodium potassium pump.
What are the symptoms of DigToxicity.
Confusion, nausea, anorexia, visual colour disturbances.
What is the antidote for DigToxicity
DigiFab antibody
Monitoring for Digoxin
(a) Routine monitoring
(b) Monitoring when patient presents with confusion and visual colour disturbances
(c) Monitoring when patient is on amiodarone or diltiazem
(d) Monitoring when patient comes in for regular blood pressure and heat rate monitoring.
(b) and (c)
What is being monitored for digoxin and why.
Serum electrolytes (K+, Mg2+ and Ca2+) as electrolyte imbalances (hypokalaemia, hypo magnesia, and hypercalcaemia) can potentiate toxicity, renal function and heart rate ( HR greater than 60 bpm).
What HR do you want patients to be at whilst on digoxin.
> 60 bpm.
Mechanism of Digoxin and its effects on cardiac tissue.
Digoxin inhibits sodium-potassium ATPase pump increasing the contractility of the heart by increase sodium and in turn calcium forming more cross-bridges to allow for powerful contractions.
Mechanism of Digoxin nodal cells.
Reduces AV node conduction via the vagus nerve.
Does digoxin affect preload/afterload/stroke volume and is it an increase or decrease or no effect.
Digoxin increases stroke volume.
Digoxin have no effect on preload.
Digoxin has no effect on after load.
Is digoxin a negative chronotrope or inotrope.
Chronotrope.
Is digoxin a positive chronotrope or inotrope.
Inotrope.
Digoxin adverse effects
Arrhythmias, possible AV block.
Digoxin: Caution and Contraindication
Heart Block.
Renal Failure.
Electrolyte imbalance
HF: patient on selective calcium channel blocker-> cardio-suppressant effects.
Pharmacokinetics of digoxin: a. Half-life? b. Excreted by which organ. c. When is steady state concentration achieved?
a. 30-40 h.
b. Kidney
c. 5-7 days
Pharmacokinetics Digoxin: a. Metabolism.
a. CYP3A4 enzymes
How is digoxin renally cleared and the clinical significance with diuretics.
Digoxin is excreted by the nephrons through tubular secretion and drugs that inhibit tubular secretion such as spironolactone and amiodarone can cause a build up of digoxin. Also renal impairment slows down elimination leading digoxin toxicity.
What drugs can impair renal function and effect digoxin excretion.
ACE-inhibitor and NSAIDs.
What drug when used concomitantly with digoxin will increase the risk of pro-arrhythmia.
Tricyclic antidepressant: block noradrenaline and adrenaline uptake increasing risk of SNS activation.
Which serotonergic receptor is implicated in pro-arrthymia.
Serotonin acts solely via 5-HT4-receptors to control human cardiac contractile … It may be assumed that 5-HT can exert a proarrhythmic effect
What drug when used concomitantly with digoxin will increase digoxin levels.
Diuretics
Proton pump inhibitor
